Magnetic core



Nov. 14, 1933. H. M. ACLY 1,935,426

MAGNETIC CORE Filed NOV. 22, 1952 Patented Nov. 14, 1933 UNITED STATESMAGNETIC CORE Harry M. Acly, Pittsfield, Mass., assignor to GeneralElectric Company, a corporation of New York Application November 22,1932 Serial No. 643,857

2 Claims.

My invention relates to magnetic cores such as are used in transformers,reactors and similar electrical apparatus. It has already been suggestedthat a magnetic core be formed by winding a strip of flat magnetic sheetmaterial into a spiral coil with a center opening for the winding orwindings. One of the advantages of such a core is that it may be formedrapidly and with simple tools. Magnetic sheet material for magneticcores is produced by a rolling process and its magnetic properties in acore are best if the path of the magnetic flux is in the direction inwhich the material was rolled. Another advantage of a magnetic core ofthe wound type is that the strip of magnetic material forming the coremay be easily arranged so that the path of the magnetic flux in allparts of the core will follow the direction in which the strip wasrolled. It is not convenient, however, to assemble a winding with amagnetic core of the wound type. The general object of the presentinvention is to provide an improved method for forming a magnetic corehaving substantially the advantages of a wound type core with theadditional advantage that it may be easily assembled with its winding orwindings.

The invention and its advantages will be explained in the followingdescription taken in connection with the accompanying drawing in whichFig. 1 shows a transformer, partly broken away, with a magnetic coreconstructed in accordance with the invention; Fig. 2 is a sectional viewon the line 22 of Fig. 1, and Figs. 3 to '7 inclusive are explanatoryviews, on a somewhat reduced scale, indicating the construction of themagnetic core shown in Figs. 1 and 2 and modified forms thereof.

Like reference characters indicate similar parts in the differentfigures of the drawing.

The transformer shown in Figs. 1 and 2 includes a two-part magnetic corewith windings 11 and 12 surrounding the adjacent sides of the two parts.Each of the two parts of the core 10 includes a large center sectionwith a smaller section at each side to fill in more completely, thecylindrical space surrounded by the windings 11 and 12. The sections ofthe core maybe alike except as to size.

Each section of the core 10 is formed from a flat strip 13 of magneticsheet material of suitable width. This strip 13 is wound flatwise into ahollow coil, preferably on a suitable form, with enough turns to givethe coil the required thickness and cross section.

In forming the core indicated in Figs. 1 to 4 inclusive, the woundmagnetic coil is separated into two parts by two cuts 14 and 15 asindicated in Fig. 3. These cuts may be made by a saw so that some of thematerial of the coil is removed and a gap is formed at each cut, thematerial removed and the length of each gap being indicated in Fig. 3between the two broken lines at each cut. The results of any previousannealing process are apt to be at least partly destroyed by cutting thecoil and the coil is therefore preferably annealed after the cuts 14 and15 are made.

The cuts 14 and 15 separate each of the turns 16 of the magnetic coilinto two sections. The turns are then reassembled around the windings 11and 12 as indicated in Figs. 1 and 2 with part of the turns reversed inposition so that the joints between their sections are displaced. Asshown in Fig. 1, alternate turns are reversed. Fig. 4 is a perspectivediagrammatic view of three successive turns showing how the jointsbetween the sections of these turns are offset after alternate turns arereversed. After the coil has been wound as shown in Fig. 3 but beforethe cuts 14 and 15 have been made, the turns are arranged end to end inthe coil with adjacent ends of the turns offset as indicated at the cut14 in Fig. 3. The 0 turns are reassembled as indicated in Figs. 1 and 4with the ends of each turn meeting each other and close together. Thus,the two parts of the coil are reassembled to form a magnetic core whichincludes two parts connected by interleaved joints as and with each turnclosed.

When reassembled as indicated in Figs. 1 and 4, each turn and thereforethe completed core is shorter than the wound coil by an amount equal tothe length of each gap formed by the cuts 14 and 15. The strip 13 istherefore wound to form a coil longer than the desired length of thecompleted core by an amount equal to the length of the gaps formed bythe cuts.

The magnetic strip 13 may also be wound as shown in Fig. 5 to form acoil with the length of one side equal to the desired length of thecom-- pleted core but with the other side longer. A cut 17 is made inthe longer side of the coil. The cut 1'7 removes some of the material ofthe coil and forms a gap in the longer side of the coil and of eachturn, the length of the gap being equal to the amount by which thelength of the coil exceeds the desired length of the completed core. Theturns are reassembled with part of them reversed in position and withthe ends of each turn formed by the cut 17 brought close together. Thereassembled turns are shown in Fig. 6 with alternate turns reversedendwise and in Fig. '7 with alternate turns reversed sidewise. With theIll single cut 17 of Fig. 5, there is the advantage that each turn inthe completed core has only a single joint instead of two joints as withthe cuts 14 and 15 of Fig. 3. With the two cuts 14 and 15, however,there is the advantage that the turns may be reassembled about thewindings 11 and 12 without bending the turns as is necessary with thesingle cut.

The invention has been explained in connection with an elongatedrectangular core and the method of producing it but the invention is ofcourse equally applicable to other forms. Other changes will also beapparent without departing from the spirit of the invention and thescope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The process of forming a hollow magnetic core, said process includingthe steps of winding a strip of magnetic sheet material flatwise to forma coil, forming a gap in at least one side of said coil, andreassembling the turns of said coil with the ends of each turn meetingend to end and the ends of said turns interleaved.

2. The process of forming a hollow magnetic core, said process includingthe steps of winding a strip of magnetic sheet material flatwise to forma coil longer than the desired completed core, forming in at least oneside of said coil a gap equal in length to the excess length of saidcoil, and reassembling the turns of said coil with the ends of each turnmeeting end to end and the ends of said turns interleaved;

' HARRY M. ACLY.

